Method of insulating coils



Feb. 16, 1932. v. 6. APPLE METHOD OF INSULATING COILS i inal Filed April19, 1929 INVENTOR Patented Feb. 16, 1932 PATENT orrlca VINCENT G. APPLE,OF DAYTON, OHIO mn'rnon or INSULATING GOILS Original application filedApril 19, 1929, Serial No. 356,586. Divided and this application filedFebruary 24, 1930. Serial No. 430,864.

This invention is a division of my copending application Serial Number356,586 and relates to an improved method of insulating coils and hasspecial reference to coils which are placed on, or about more or lesscomplex structures of other materials.

An object of the invention is to insure more and better insulationbetween the individual turns of coils than has been possible by methodsheretofore employed.

A second object is to provide means and a procedure which will carry outthe first object with minimum expenditure of labor and material.

Another object is to provide a process and apparatus whereby the more orless porous covering of magnet wire may be saturated and coated with anaccurately determined layer of suitable insulating material in liquidform and partially dried before it is wound into coils, to the end thatthere would be no excess of the liquid present which ma get on the spoolor core upon which the coil is placed, or on other surfaces of thestruc- 2 ture, or in openings therein, where insulation would beobjectionable and where its removal would present almost insurmountabledifficulties after it became solid.

Another object is to employ insulating maso terial of such a nature, andto so apply it between the turns of the coils as will provide astructure wherein the winding is capable of withstanding great abuse andconsiderable distortion, to the end that a layer of plastic insulationmay be safely pressure molded thereabout without injury thereto whensuch a covering is deemed desirable.

That these and many other objects and meritorious features of theinvention meattained by the procedure hereinafter outlined and describedwill be readily apparent to one skilled in the art from a considerationof the following description when taken in conjunction with the drawingswhich illustrate a dynamo electric machine field element made accordingto the principles involved in my invention.

In the drawings, Fig. 1 shows apparatus for applying a coating of liquidinsulation to a magnet wire which already has a covering of more or lessporous insulation.

Fig. 2 shows apparatus for winding the wire on a temporary spool whereit may beconiie partially dry before it is wound into cm s.

Fig. 3 shows a set of field coils wound from magnet wire treated by myprocess.

Fig. 4 shows six sets of the coils as they appearwhen they are in thefield core, the core having secured thereto brush and line terminals towhich the coil ends are joined.

Fig. 5 shows a mold within which the field structure shown in Fig. 4 issupported, there being sufficient additional space within the mold toreceive a quantity of plastic insulation to form a cover or housingabout the coils and terminals.

Similar numerals refer to similar parts throughout the several views.

In the construction of wound electrical devices which are intended towithstand any considerable electrical pressure it is the usual practiceto wind the spools, or cores as the case may be, with conductive wirehaving a covering of more or less porous insulation, usually a fibrousmaterial such as cotton, silk, asbestos, etc. and subsequently toimmerse the wound core in a liquid insulating material and then applypressure to the container to force the liquid to enter the porouscovering of the wires and other interstices of the winding.

An objection to this method of insulating coils by impregnation is thatoften, after a coil is wound, and before it is impregnated with theliquid insulation, there are turns of the wire within the coil which arepressed so closely together, one turn against another, that the fibrouscovering is almost, and sometimes quite, cut through, leaving adjacentturns in electrical contact, the condition occurring most frequently ofcourse in a winding such as is employed on an armature, where many ofthe turns cross, one over the other. Obviously, a sufficiently highpressure may force a liquid insulation to the innermost turns of thewound coil, but there is no reason to believe that any amount ofpressure on namo electric machine field element I have selected toillustrate my inventlon,

the container will force the liquid to enter and spread apart thoseturns which are already in too intimate contact.

Anotherobjection to the method of insulating Wound devices byimpregnation, is that in a great many cases the coils must be wounddirectly on the core, so that when afterward the coils are to beimpregnated, the entire structure comprising the core, the coils andtheir terminals is necessarily immersed in the li uid insulation.

ow' this would involve no great hardship in the case of a simple coil,but in a more complex structure, such for instance as the dywhich theliquid would cover the binding posts and brush terminals, would enterthe central bore which must afterward clear an armature, and willpenetrate and fillv the bolt holes which extend longitudinally throughthe core, and while tools may be made to exclude the insulation fromthese parts while impregnation is being effected, there is afterwardsubstantially as great difiiculty in removing the surplus insulationfrom these tools as there would have been in removing it from thesurfaces and holes of the wound element protected by them, for it is awell known fact that some of the best known liquid insulating materialshave also the greatest adhesive properties.

Because they overcome the foregoing and many other objections to theconventional method of insulating coils, the hereinafter describedprocedure is considered of great value in the art.

The coating apparatus Fig. 1 has a base 10 upon which is mounted atubular'body 11, divided near its middle into two parts 12 and 13, theparts being held together by a threaded sleeve 14.

Body 11 is hollow, the space within being divided into two chambers 15and 16 separated by a plug 17, which may be inserted and removed whenthe two parts 12 and 13 are separated by the removal of sleeve 14.

Plugs 18, held in place by screw caps 19, close the outer ends ofchambers 15 and 16. Both plugs 18 as well as plug 17 have holes,extending longitudinally therethrough, of a diameter equal to that ofthe wire to be coated. These plugs are preferably made from a materialof a more or less yielding nature so as to permit the passage of a knotor a splice without undue strain on the wire. Cork has been found to besatisfactory both asto yielding qualities and as to wear, al though asoft rubber plug having a small longitudinal split metal bushingimbcdded at its center is equally desirable.

A tank 20 extends from body part 12 and communicates with chamber 15.Upon removal of filler plug 21 the tank may be partly filled with liquidinsulation 22 as shown.

her 16. The ends through insulating bushings 30 as shown. A

An air pump 23 has its discharge valve 24 connected by pipe 25 to tank20 and its suction valve 26 connected by pipe 27 to chamber 16. The pump23 is operated to create a partial vacuum in chamber 16 and pressure inthe space 28 above the liquid 22 in tank 20.

A coil 29 of electrical resistance wire is suspended within, but doesnot touch chamof coil 29 are brought out second coil 31 is supported onmetal brackets 32 extending. from base 10. An electric current is madeto flow through coils 29 and 31 when wire is being coated.

Magnet wire 33 comprising conductive wire covered with a thin layer ofcotton or similar absorptive material is drawn from its spool 34 throughone plug 18 into vacuum chamber 16 through coil 29 out of chamber 16through plug 17 into the liquid insulation 22 in chamber 15 and outthrough the other plug 18 and coil 31. a

\Vhen the wire 33 enters chamber 16, the partial vacuum, together withthe heat generated by resistance coil 29, takes whatever moisture theremay be from the porous cover, so that it enters chamber 15 dry, and withthe pores of the fibrous covering under partial vacuum, and inasmuch asliquid 22 is under pressure it more readily penetrates all of the poresof the fibrous covering.

As the wire emerges from chamber 15 through plug 18 the surplus liquidis stripped off and retained in the chamber and the coating is given adefinite size, depending of course on the accuracy maintained in theopening through plug 18. As the wire passes through heating coils 31,the liquidinsulation is partly dried.

Whether the wire is now wound on a spool suitable for keeping it instorage, or whether it is wound directly on the cores or into finishedcoils, depends somewhat on the nature of the winding.

lVhere an electrical device is of such a nature as to require to be handwound, or where the winding is more or less tedious and apt to takewiremore slowly than it comes from the coating apparatus, or where itissimple and takes wire more coated, it may be advantageous to windthewire into a storage coil.

It will of course be understood that when the wire comes from theheating coil 31, the liquid insulation is not completely baked out, yetit is dried sufliciently to make the coating tough and somewhat pliable,and it will of course be still slightly sticky, so that, in order tosuccessfully store it, the reeling apparatus and the storage coil whichit produces are necessarily of special construction.

The reeling apparatus Fig. 2 consists of a spindle 35 revolvable bypulley 36 in bearings 37 mounted on base 38. A worm 39 on the end of thespindle 35 drives wormwheel 40 rapidly than it can be 1 6 whereby block41 carrying wire guide 42 is reciprocated through, connecting rod 43.Worm 39 preferably has multiple threads of coarse pitch and wormwheel 40is preferably of small diameter and few teeth so that guide 42 may bereciprocated through a complete cycle in relatively few turns of spindle35.

Because of this coarse pitch the wire is wound on the nose 45 of thespindle with wide space between turns and the turns of one layercrossing the turns of the layer beneath at considerable angle. Such acoil is commonly called a honey-comb coil, and is here wound in thisshape, principally to prevent too great contact area and consequentadhesion between successive turns of a layer and between successivelayers when the wire in unwound to be rewound into a permanent coil.Fig. 3 shows permanent coil 46 wound in three interconnected parts 47,48and 49 which adapts it to a slotted core 50, Fig. 4, which I used forthe field element herein selected for illustration, the beginning 51 ofthe inner section 47 being adapted to connect to one of the lineterminals, and the end 52 of the outer section 49 being adapted toconnect to one of the brush terminals.

Fig. 4 shows the field core 50 with six of the insulation treated coils46 in place. Line terminals 53 and brush terminals 54 are insulated fromthe core though secured thereto by screws which pass through insulationlined holes in the core. The proper coil ends are electrically joined toterminals 53 and 54, as shown. The structure comprising core 50, coils46, line terminals 53 and brush terminals 54 may be designated as awhole by numeral 55.

The structure 55 is now placed in a mold 56, Fig. 5, the essential partsof which are the outer body portion 57 having lateral pulls 58 which maybe withdrawn from the completed molding to form brush pockets therein,the inner body portion 59 with the opening 60 passing therethrough andthe plunger 61 snugly fitted to the opening 60. The opening 60 may becalled the stock chamber since it olds the loose molding compound 62prior to the molding operation and the space 63 between body portions 57and 59 may be called the molding chamber since the stock 62 iscompressed into it.

It will be seen that the stock chamber 60 shown with plunger 61 slightlyentered, is in effect separate from the molding chamber 63, which is toform the finished housing, and that the end wall 64 of body portion 57in effect forms a bottom for the stock chamber 60, so that movement ofmoldable material from the stock chamber 60 into the molding chamber 63must be laterally of the movement of the plunger which forces thematerial out (I: the stock chamber into the molding cham- The reason forso constructing the mold and the manner of using it, is fully disclosedin my copending application Serial No.

267,782 filed April 5th, 1928, and consists compound absorbs sufficientheat from the mold to become fluid and so flow laterally from under theplunger into the molding chamber 63 and there be compressedhydraulically about the coils and to the contour of the interior 63 ofthe molding chamber, then allowing the compound together with theinsulation coating previously put about the individual turns of the coilto be hardened from the heat remaining in the mold.

Because of the manner in which the molding pressure comes on thewinding, that is, substantially equal in all directions thereon, verylittle distortion of the coils results, and, because of the manner inwhich the individual turns of the winding are insulated, no ill effectresults from such distortion of the coils as may occur.

The advantages of my improved method are numerous. First, the thicknessof the insulation between turns of the coils is accurately controllableand does not depend on the space which may be left between turns of acoil which has been wound of cotton or similarly covered wire andafterward impregnated with a fluid insulation as in common practice;second, the liquid insulating material is conserved, since it is kept ina tight- 1y closed receptacle while it is being applied to the wire,instead of in an open tank where a considerable portion is always lostby Evaporation and consequent adhesion to the rial is not only placedwhere it will have the greatest effect but it is kept off of thoseportions where its presence would be objectionable, as on portions ofthe core and terminals, and from openings therein.

While it has been heretofore proposed to so impregnate and harden awound coil as to enable it to resist distortion when a layer of plasticinsulation is afterward molded thereabout, the herein described processcomprises new steps whereby I succeed in so insulating the turns of acoil, one from another, that the distort-ion which results when thefurther step of molding a casing of plastic insulation is afterwardtaken is withstood with no ill effect, and while the entire methodconsists of a plurality of steps taken in a given sequence, with toolshaving a number of novel features, it will be apparent that methodscomprising less than the entire number of steps indicated, and apparatushaving less than the entire number of features, may in many cases beemployed and will produce a new and useful result, for instance, on verysmall wire or where the covering on the wire is very porous, or when theliquid insulation is very thin, keeping pressure on the liquid, orpassing the wire through Vacuum, may be dispensed with, or when the wireis drawn through the coating apparatus very slowly the heating elementsmay be omitted, and while the preferred form of wound element comprisesa jacket of plastic insulation molded about the pre-insulated coils, thestructure may be heated so that the liquid insulation on the wirecomposing the coils will be baked, whereupon the structure may bemounted in a separately made housing of molded insulation or of othermaterial.

Holding this View of the scope of the invention,

I claim 1. The method of making a coil from conducting wire having aporous covering, which consists of drawing the wire into and out of snugfitting openings in an otherwise closed receptacle containing liquidinsulation, the wire passing through said insulation, applying pressureto the insulation Within said receptacle as the wire passes through,applying heat to said wire after it comes from said receptacle to partlydry the insulationforced into said covering by said pressure, Windingthe wire into a coil, placin the coil into a mold, heating the mold tofinish drying the insulation, then pressing a jacket of plasticinsulation around the coil.

2. The method of making a coil for electrical use, from conducting wirehaving a covering of porous insulation, which consists of saturating andcoating the porous covering with liquid insulation, winding the wireinto a coil, placing the coil in a mold, heating the coil and moldtogether until the coating becomes a rigid mass, placing a measuredquantity of plastic insulating compound in the heated mold, allowing itto soften from the heat of the mold, then compressing it about the rigidcoil.

In testimony whereof I afiix my si nature.

VINCENT G. APi LE.

